From d52f1d0570aa59e6dc7ff4034936ca3c1f85b664 Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Sun, 24 Dec 2023 09:23:38 +0100
Subject: [PATCH] Day 22: slow but straightforward. off-by-three errors.

---
 2023/43.pl | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2023/44.pl | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 179 insertions(+)
 create mode 100755 2023/43.pl
 create mode 100755 2023/44.pl

diff --git a/2023/43.pl b/2023/43.pl
new file mode 100755
index 0000000..da408f2
--- /dev/null
+++ b/2023/43.pl
@@ -0,0 +1,91 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+use experimental 'multidimensional';
+
+my @bricks = map { [ /\d+/g ] } <>;
+my %seen;
+sub set_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		$seen{$x,$y,$z} = 1;
+	} } }
+}
+
+sub clr_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		undef $seen{$x,$y,$z};
+	} } }
+}
+
+sub can_fall {
+	my ($b) = @_;
+
+	return undef if !$b->[5];
+	my $z = $b->[5]-1;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+		return undef if $seen{$x,$y,$b->[2]-1};
+	} }
+	return 1;
+}
+
+set_brick($_) for @bricks;
+
+while (1) {
+	my $fallen;
+	my $i = 0;
+	for my $b (@bricks) {
+		$i++;
+		next if !can_fall($b);
+		# say "falling $i (@$b)";
+		clr_brick($b);
+		$b->[2]--; $b->[5]--;
+		set_brick($b);
+		# say "fallen  $i (@$b)";
+		$fallen++;
+	}
+	last if !$fallen;
+}
+
+my $count = 0;
+my (%supported, %supports);
+for my $bi0 (0 .. $#bricks) {
+	my $b0 = $bricks[$bi0];
+	my $cnt = 0;
+	BRICK:
+	for my $bi1 (0 .. $#bricks) {
+		next if $bi0 == $bi1;
+		my $b1 = $bricks[$bi1];
+		# say "possibly supports $bi0 (@$b0) $bi1 (@$b1)";
+		next if $b1->[2] != $b0->[5]+1;
+		for my $x0 ($b0->[0] .. $b0->[3]) {
+		for my $x1 ($b1->[0] .. $b1->[3]) {
+			next if $x0 != $x1;
+			for my $y0 ($b0->[1] .. $b0->[4]) {
+			for my $y1 ($b1->[1] .. $b1->[4]) {
+				next if $y0 != $y1;
+				$supports{$bi0}->{$bi1}++;
+				$supported{$bi1}->{$bi0}++;
+				next BRICK;
+			} }
+		} }
+	}
+}
+SBRICK:
+for my $bi0 (0 .. $#bricks) {
+	for my $bi1 (keys %{ $supports{$bi0} }) {
+		next SBRICK if keys(%{ $supported{$bi1} }) == 1;
+	}
+	$count++;
+}
+
+say $count;
diff --git a/2023/44.pl b/2023/44.pl
new file mode 100755
index 0000000..e8ee0c7
--- /dev/null
+++ b/2023/44.pl
@@ -0,0 +1,88 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+use experimental 'multidimensional';
+$; = ';';
+
+my @bricks = map { [ /\d+/g ] } <>;
+my %seen;
+sub set_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		$seen{$x,$y,$z} = 1;
+	} } }
+}
+
+sub clr_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		undef $seen{$x,$y,$z};
+	} } }
+}
+
+sub can_fall {
+	my ($b) = @_;
+
+	return undef if !$b->[2];
+	my $z = $b->[2]-1;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+		return undef if $seen{$x,$y,$z};
+	} }
+	return 1;
+}
+
+set_brick($_) for @bricks;
+
+while (1) {
+	my $fallen;
+	my $i = 0;
+	for my $b (@bricks) {
+		$i++;
+		next if !can_fall($b);
+		# say "falling $i (@$b)";
+		clr_brick($b);
+		$b->[2]--; $b->[5]--;
+		set_brick($b);
+		# say "fallen  $i (@$b)";
+		$fallen++;
+	}
+	last if !$fallen;
+}
+
+my $sum;
+SBRICK:
+for my $bi0 (0 .. $#bricks) {
+	my @bricks1 = map { [ @$_ ] } @bricks;
+	splice @bricks1, $bi0, 1;
+	%seen = ();
+	set_brick($_) for @bricks1;
+	my %f;
+	while (1) {
+		my $fallen;
+		my $i = 0;
+		for my $bi1 (0 .. $#bricks1) {
+			my $b1 = $bricks1[$bi1];
+			next if !can_fall($b1);
+			# say "falling $i (@$b1)";
+			clr_brick($b1);
+			$b1->[2]--; $b1->[5]--;
+			set_brick($b1);
+			# say "fallen  $bi1 (@$b1)";
+			$fallen++;
+			$f{$bi1}++;
+		}
+		last if !$fallen;
+	}
+	# say "falling $bi0 (@{ $bricks[$bi0] }) falls ", join(',',sort keys %f);
+	$sum += keys %f;
+}
+
+say $sum;
-- 
2.43.0